Leaf extracts of cultivated cardoon as potential bioherbicide

Increasing concerns about negative herbicides effects on the environment and the growing interest in organic agriculture demand for alternative weed control methods. This work aims to evaluate the phytotoxicity of different cultivated cardoon (Cynara cardunculus L. var. altilis DC.) leaf extracts on seed germination of four weeds (Amaranthus retroflexus L., Portulaca oleracea L., Stellaria media (L.) Vill., and Anagallis arvensis L.) commonly found in Mediterranean Basin, and to identify the compounds responsible for the extracts’ inhibitory activity. The extracts were obtained from dried, lyophilized and fresh leaves treated with three different solvents: water, methanol and ethanol. Citric acid was added to each solvent to check if the yield extract could be affected by pH modification. All extracts showed inhibitory effects on seed germination and mean germination time in all weeds, compared to control. The ethanolic extracts obtained by lyophilized leaves induced completely inhibition of seed germination in all weeds. Good results were also observed by using dried leaves, representing a valid alternative to lyophilized ones in terms of cost management. The HPLC analysis revealed that major compounds were caffeoylquinic acids, followed by flavones (apigenin and luteolin derivatives) and by the sesquiterpene lactone cynaropicrin. These results indicate that cultivated cardoon leaf extracts could present a good potential bioherbicide.